Micro-electro-mechanical systems (MEMS) gyroscopes and accelerometers, such as disclosed in U.S. Pat. Nos. 6,725,719 and 6,859,751, are generally planar instruments. Due to their very small size, and materials and methods of construction, such MEMS inertial instruments are relatively sensitive to ambient temperature and other environmental factors. These sensitivities makes them relatively unstable. Accordingly, it has been necessary to extensively test such instruments under a variety of conditions in order to develop a priori compensation schemes that can then be built into systems employing such instruments. This testing is time consuming and expensive, and also may not anticipate every possible condition that the instrument may be exposed to, which can lead to errors.
The accuracy of Microelectromechanical Systems (MEMS) gyroscopes and accelerometers depends on the stability of their bias. Bias is the non-zero instrument output in the absence of input. The bias has deterministic and random components. Each deterministic component can be related to a cause, which potentially can be controlled. Random components can be traced to a cause but cannot be controlled. The pertinent random component for this invention is the 1/f noise, which is related to intrinsic shot noise in the electronics and Brownian motion due to atoms colliding with the mechanical structures. The bias, as an offset value, can vary from turn-on to turn-on. The deterministic component can vary as a drift.
The problem is that under motion, the instrument bias is undistinguishable from the signal generated by the motion, hence the output in incorrect and the MEMS instrument is impractical and requires continuous correction to be useful.